The present invention is directed to an improvement in cutting tools related to coolant delivery. More particularly, the present invention is directed to at least one coolant delivery channel formed in an external cylindrical surface of a cutting tool.
Delivery of coolant to the interface between the cutting edge of a cutting tool and the workpiece where material removal is taking place is critical. If the temperature of this interface is not maintained in a safe zone, i.e., if the temperature is allowed to rise due to inadequate supply of coolant, the cutting edge will deteriorate rapidly and the useful life of the tool will be adversely affected. In addition, coolant is needed to assist in chip evacuation, reducing build-up edge and preventing re-cutting of the chips.
The methods of delivering coolant to date are less than satisfactory. To spray the coolant at the interface has a number of problems. Firstly, it ingests air reducing the effectiveness of the coolant. Second, if the approach angle of the coolant stream is too high, a portion of the coolant will simply splash off the face of the tool or workpiece having little if any effect. Further, with a high approach angle, there is an increased likelihood that the coolant will not contact the interface at all but will, instead, splash off the back side of the chip being removed from the workpiece. This will not have an appreciable impact on the temperature of the cutting tool/workpiece interface. Accordingly, the cutting edge is at risk to reach dangerously high temperatures that will permit accelerated degradation thereof.
One proposed solution to this problem is to incorporate a passageway axially through the center of the tool. This significantly compromises the strength of the tool increasing the incidence of breakage. In addition, it delivers the coolant out the end of the cutting tool which may or may not be the optimum location for coolant delivery. For example, most drills and milling tools, including end mills, would benefit more from coolant delivered to the cutting edges. One attempt to overcome this defect is set forth in U.S. Pat. No. 3,037,264 to Mossberg, for example. Mossberg cuts intersecting radially directed passageways from the central passageway toward the cutting flutes. This will tend to deliver coolant to a more useful location. However, the lateral passageways are subject to clogging by chips; further, the removal of additional material further compromises the integrity of the cutting tool resulting in a higher incidence of failure; finally, the high angle of approach (roughly 90xc2x0 to the interface) ensures a high percentage of the coolant will impact the outer face of the chip so that it does not meaningfully reduce the temperature of the cutting interface. In addition, manufacturing this tool with the lateral exit holes is a very expensive operation making the tool cost and economics of its use prohibitive. Consequently, sales are minimal.
The improved coolant delivery system of the present invention, which is designed to be used with a cutting assembly which cuts by fastening an elongated cutting tool having a cylindrical wall with at least one cutting flute in the spindle of a rotary power tool where coolant is fed through the spindle for use by the cutting tool, the coolant delivery system comprising at least one channel cut in the cylindrical wall of the elongated cutting tool to convey coolant from the spindle to the cutting flutes of the elongated cutting tool. The delivery system preferably has at least as many, or more, coolant delivery channels as the cutting tool has cutting flutes. Some versions of the tool will require two or more channels per flute to deliver adequate coolant along the full length of the cutting edge. The delivery channels may be configured either as straight, or, if the cutting flutes are helical, the channels may have a helix angle which is equal to, less than or greater than the helix angle of the flutes. By way of the example, the helix angles of the delivery channels may be selected from the group of angles between 0xc2x0 and 60xc2x0. The performance of the channels is enhanced by varying the width and/or the depth of the channel to optimize fluid flow.
Various other features, advantages and characteristics of the present invention will become apparent to one of ordinary skill in the art after a reading of the following specification.